Designed by Bell Aircraft, it had an innovative layout, with the engine installed in the center fuselage, behind the pilot, and driving a tractor propeller via a long shaft. It was also the first fighter fitted with a tricycle undercarriage. Although its mid-engine placement was innovative, the P-39 design was handicapped by the absence of an efficient turbo-supercharger, limiting it to low-altitude work. Together with the derivative P-63 Kingcobra, the P-39 was one of the most successful fixed-wing aircraft manufactured by Bell.
In September 1940, Britain ordered 386 P-39Ds (Model 14), with a 20 mm (.79 in) Hispano-Suiza HS.404 and six .303 in (7.7 mm), instead of a 37 mm (1.46 in) cannon and six 0.30 in (7.62 mm) guns. The RAF eventually ordered a total of 675 P-39s. However, after the first Airacobras arrived at 601 Squadron RAF in September 1941, they were promptly recognized as having an inadequate rate of climb and performance at altitude for Western European conditions. Only 80 were adopted, all of them with 601 Squadron. Britain transferred about 200 P-39s to the Soviet Union.
Another 200 examples intended for the RAF were taken up by the USAAF after the attack on Pearl Harbor as the P-400, and were sent to the Fifth Air Force in Australia, for service in the South West Pacific Theatre.
By the time of the Pearl Harbor attack, nearly 600 P-39s had been built. When P-39 production ended in August 1944, Bell had built 9,558 Airacobras, of which 4,773 (mostly −39N and −39Q) were sent to the Soviet Union through the Lend-Lease program. There were numerous minor variations in engine, propeller, and armament, but no major structural changes in production types, excepting a few two-seat TP-39F and RP-39Q trainers. In addition, seven went to the U.S. Navy as radio-controlled drones.
Trials of a laminar flow wing (in the XP-39E) and Continental IV-1430 engine (the P-76) were unsuccessful. The mid-engine, gun-through-hub concept was developed further in the Bell P-63 Kingcobra.
A naval version with tail-dragger landing gear, the XFL-1 Airabonita, was ordered as a competitor to the Vought F4U Corsair and Grumman XF5F Skyrocket. It first flew 13 May 1940, but after a troublesome and protracted development and testing period, it was rejected.
Operational historyThe Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Russian theaters. Because its engine was only equipped with a single-stage, single-speed supercharger, the P-39 performed poorly above 17,000 feet (5,200 m) altitude. In both western Europe and the Pacific, the Airacobra found itself outclassed as an interceptor, its earliest proposed role, and the type was gradually relegated to other duties. It often was used at lower altitudes for such missions as ground strafing.
Soviet pilots appreciated the cannon-armed P-39 primarily for its air-to-air capability. A common Western misconception is that the Bell fighters were used as ground attack aircraft.
The Soviets developed successful group aerial fighting tactics for the Bell fighters and scored a surprising number of aerial victories over a variety of German aircraft. Soviet P-39s had no trouble dispatching Junkers Ju 87 Stukas or German twin-engine bombers and matched, and in some areas surpassed, early and mid-war Messerschmitt Bf 109s. The usual nickname for the Airacobra in the VVS was Kobrushka ("little cobra") or Kobrastochka, a portmanteau of Kobra and Lastochka (swallow), "dear little cobra"."One of the enduring myths regarding the P-39/P-63 in Soviet use is that because of its armament, in particular the 37mm nose cannon, it excelled as a ground-attack aircraft, even a 'tank buster.' In translating and preparing this manuscript for publication, I have had the opportunity to peruse several Russian-language sources. Mentions of the employment of this aircraft in the ground-attack role are so rare in these sources as to be exceptional ... The 'tank buster' myth has its roots in the misunderstanding of the general wartime role of the Red Air Force and in the imprecise translation of specific Russian-language terms that describe this role. The specific Russian-Language term most often used to describe the mission and role of the Airacobra-equipped Red Air Force fighter units, in this manuscript and other Russian-language sources , as prikrytiye sukhoputnykh voysk [coverage of ground forces]... Frequent misunderstanding in this country as to the combat role of the P-39 in Soviet use is based in part on imprecise translation of the term prikrytiye sukhoputnykh voysk to 'ground support'. The latter term as it is understood by many Western military historians and readers, suggests the attacking of ground targets in support of ground troops, also called "close air support." Soviet Airacobra pilot ever strafe a German tank? Undoubtedly. But this was never a primary mission or strong suit for this aircraft."—Soviet Army Colonel Dmitriy Loza, Loza and Gebhardt 2002, pp. 15–16.
The first Soviet Cobras had a 20 mm Hispano-Suiza cannon and two heavy Browning machine guns, synchronized and mounted in the nose. Later, Cobras arrived with the M-4 37 mm cannon and four machine guns, two synchronized and two wing-mounted. "We immediately removed the wing machine guns, leaving one cannon and two machine guns," Golodnikov recalled later. That modification improved roll rate by reducing rotational inertia. Soviet airmen appreciated the M-4 cannon with its powerful rounds and the reliable action but complained about the low rate of fire (three rounds per second) and inadequate ammunition storage (only 30 rounds).
The Soviets used the Airacobra primarily for air-to-air combat against a variety of German aircraft, including Bf 109s, Focke-Wulf Fw 190s, Ju 87s, and Ju 88s. During the battle of Kuban River, VVS relied on P-39s much more than Spitfires and P-40s. Aleksandr Pokryshkin, from 16.Gv.IAP, (16th Guards Fighter Aviation Regiment) claimed 20 air victories in that campaign. Pokryshkin, the second-highest scoring Allied ace (59 air victories plus six shared) flew the P-39 from late 1942 until the end of the war (though rumors exist that he changed in late 1944 to a P-63 Kingcobra).
scored 44 victories flying Airacobras. The majority of his kills were achieved in P-39N-0 number 42-8747 and P-39Q-15 number 44-2547. During the war, he was awarded the Order of Lenin, the Order of the Red Banner (four times), the Order of Alexandr Nievskii, the Order of Patriotic War 1st Class and the Order of the Red Star (twice). This is the highest score ever attained by any pilot with any American-made aircraft.
The United States did not supply M80 armor-piercing rounds for the autocannons of Soviet P-39s—instead, the Soviets received 1,232,991 M54 high-explosive rounds which the Soviets used primarily for air-to-air combat and also against soft ground targets. The VVS did not use the P-39 for tank-busting duties.
A total of 4,719 P-39s were sent to the Soviet Union, accounting for more than one-third of all U.S. and UK-supplied fighter aircraft in the VVS, and nearly half of all P-39 production. Soviet Airacobra losses in 1941–45 were 1,030 aircraft (49 in 1942, 305 in 1943, 486 in 1944 and 190 in 1945).
Airacobras served with the Soviet Air Forces as late as 1949, when two regiments were operating as part of the 16th Guards Fighter Aviation Division in the Belomorsky Military District.
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